Photosynthesis of organic compounds in the atmosphere of Jupiter

Abstract

THE substances responsible for the red-brown colours of the atmosphere of Jupiter are the source of much debate. Initially it was suggested that the coloured materials are HCN oligomers and polymeric organic nitriles which are formed during electrical storms on Jupiter^1,2. This model has been criticised on two grounds: first it seems unlikely that there could be sufficient lightning on Jupiter to account for the intense red-brown coloration and second, the electrical storms could only take place in the lower atmosphere of Jupiter, where condensation of water vapour takes place, and therefore there would have to be some means of transporting the compounds above the NH₃ ice clouds³. Another postulate is that the colour comes from elemental sulphur and polysulphides formed by the photolysis of H₂S (ref. 4). Organic compounds may also be produced when H₂S is photolysed in the presence of CH₄ and the other hydrocarbons present in the Jovian atmosphere^5,6. Since neither H₂S nor NH₄SH has been detected in the upper atmosphere of Jupiter it is necessary to postulate either that the rate of H₂S photolysis is much faster than its rate of transport to the upper atmosphere, or that sunlight reaches the lower atmosphere through gaps in the ammonia ice clouds and the sulphur and polysulphides so formed are then transported to the upper atmosphere. A third postulate suggests that both organic compounds and polysulphides may be formed by a bombardment of the atmosphere with high energy protons and electrons⁷.